False pregnancy can occur in an intact female dog regardless of whether or not she has been mated. It occurs 4-9 weeks after her estrus, or heat cycle. False pregnancies do not happen in spayed female dogs.
A false pregnancy can occur at any age and does not necessarily follow every estrus. The severity and duration of clinical signs can vary not only from dog to dog but also from one heat cycle to the next in the same dog.
The exact cause of a false pregnancy is unknown. What is understood is that after an estrus cycle, a female dog’s ovaries begin to produce hormones whether she is pregnant or not. These hormones prepare the uterus to receive fetuses and maintain the pregnancy.
If a dog does not become pregnant, after 4-6 weeks these hormone levels decrease, and this can sometimes send a signal to the body stimulating mammary gland development and other symptoms of a false pregnancy. Some female dogs will also show symptoms of false pregnancy 3-4 days after a spay surgery when the ovaries and uterus have been removed.
The diagnosis of false pregnancy is often based on history and ruling out other possible causes for the clinical signs that your dog is showing. Blood work can be used to rule out things like pyometra, which is a life-threatening infection in the uterus. Ultrasound can be used to diagnose if your dog is pregnant after day 28 of pregnancy. Radiographs (x-rays) can also diagnose pregnancy, but not until day 45.
Mild cases of false pregnancy do not require treatment and will resolve in about 2-3 weeks. If the dog appears physically ill, symptomatic treatment can be started. This can include antiemetics to decrease vomiting and anorexia, or diuretics to reduce mammary secretions and fluid retention.
Your vet may also recommend using warm or cold packs on the mammary glands to decrease inflammation and minimize the stimulation that promotes lactation. If your dog is acting very anxious or aggressive, your vet may prescribe sedatives or tranquilizers. In rare, very serious cases, hormonal treatment may be required.
Surgical removal of the ovaries and uterus - a spay surgery - is used to prevent future episodes of false pregnancy behavior. Ideally, you should wait until all symptoms have completely resolved before spaying. If your dog undergoes a spay surgery while she is experiencing false pregnancy signs, the signs may continue for several weeks after surgery.
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